It is odd. And extremely frustrating when the office manager at shul puts you on the rotation 3 times instead of two, and gets angry at you for asking about it! That was when we quit that shul. Luckily, we live in an urban area with a large Jewish community so we have our choice of other shuls. Unfortunately, our favorite is not walking distance from our house, and we have to think about our daily commutes... so meanwhile we've been those annoying people who come semi regularly but aren't members. (But we do donate on occasion)